Image display device and method for displaying an image on the basis of a plurality of image signals

ABSTRACT

Image signals input terminals are selected by a selector. The image signals are combined and displayed on the same screen of a display device. The display screen includes one main screen and a plurality of sub screens. In the case where a moving image is displayed on the main screen, images displayed on the sub screens are updated when the moving image displayed on the main screen are in a still state. The modes of the image signals are detected only when they are input for the first time, the process performed upon the image signals input after that is controlled in accordance with information stored in a memory.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an image display device andmethod for displaying an image signal selected from a plurality of imagesignals input from the outside and switching the image signal beingdisplayed as desired.

[0003] 2. Description of the Related Art

[0004] In the art of image display devices, it is known to select one ofa plurality input image signals using a mechanical or electrical switchand display the selected image signal.

[0005]FIG. 14 is a block diagram illustrating an example of such aconventional image display device.

[0006] In FIG. 14, a plurality of personal computers (PCs) 101, a DVD(digital versatile disc) player 102, and a terminal 103 for outputtingan image signal are connected to a display device 105 via an imagesignal selection switch (SW) 104. The display device 105 displays animage signal selected by the image signal selection switch 104, that is,an image output from one of the personal computers 101 or the DVD player102.

[0007] When the convention image display device is used, in a meeting orthe like, to display images such that an image signal is selected fromthose output from a plurality of personal computers or terminal devicesconnected to the display device and the selected image signal isdisplayed using a large-screen display device such as a projector, thereis a possibility that the image signals output from the PCs or theterminal devices are based on different standards, and thus it isrequired that the image display device should have the capability ofhandling the image signals based on various different standards. Even ifthe image display device has such a capability, the image display devicecan still have a problem. That is, when the input image signal isswitched, the image mode is detected from the synchronization signals HD(horizontal deflection) and VD (vertical deflection) after the new inputsignal has become stable, and then the oscillation frequency of a PLLcircuit is determined and the displaying position and the sampling phaseare adjusted. Therefore, it takes a long time for the displayed image tobecome stable. The displayed image can have a disturbance during such atransient period.

[0008] Another problem of the conventional image display device is inthat only one image signal selected from the plurality of input imagesignals can be displayed at a time, and thus it is impossible to knowthe contents of the other image signals.

[0009] When a projector is used in a meeting to display an image signalselected from image signals output from a plurality of PCs and the imagebeing displayed is switched as required, it is impossible to know thecontents of the image signals other than the image signal beingcurrently displayed. This is inconvenient for the attendants at themeeting. The image signals output from the respective PCs can bedifferent in characteristics (such as a frequency) from each other, ittakes a long time to achieve a stable state after switching the imagebeing displayed even if the display device has the multiscan capability,and the image being displayed can be disturbed. In particular, in ameeting or education system in which a large-screen display device isused to display an image signal selected from the image signals outputfrom a plurality of PCs and switch the image being displayed as desired,the above-described problems are serious.

[0010] In recent years, the quick and great advance in the technology ofmobile terminal devices have made it possible for ones to storenecessary data in their own mobile terminal devices and to obtain databy accessing a server via their own terminal devices. This allows onesto do jobs without having restrictions in terms of time and place, andthus greater productivity of jobs can be achieved. When a meeting isheld in such an environment, attendants want to make a discussion on thebasis of data output from their own mobile terminal devices.

[0011] However, in the conventional image display device, the simpleselection switch 104 used to connect a plurality of devices causes thefollowing problems. That is:

[0012] 1) Complicated and troublesome cable connections are required. Inparticular, the small size of mobile terminal devices results in alimitation in the type of cable. Furthermore, in many cases, anadditional module is required for connection to the video outputterminal. This makes the cable connection more complicated andtroublesome. A connection to a projector for displaying on a largescreen an image output from a PC in a meeting is generally made using aVGA (Video Graphic Array) cable having a D-Sub (Subminature-D) 15-pinconnector with a large size. The large connector size and the recenttendency of projectors to have reduced sizes limit the number of inputterminals of the projectors up to two, one of which is generally usedfor connection with a PC and the other is used as a video inputterminal. Although some high-end projectors have two or three inputterminals for connection with PCs and for video inputs, respectively,the number of devices which can be connected is still limited.

[0013] 2) When a VGA cable is used, the VGA cable having a largediameter and a small length on the order of 2 m limits the location of amobile terminal device. Thus, an attendant has to move his/her mobileterminal device to a location which allows the terminal device to beconnected to the cable whenever it is required to output data in ameeting. Thus, time is spent uselessly for connection, and theconnecting operation often breaks the meeting.

[0014] 3) It takes a long time to achieve a stable state in thedisplaying of an image after switching the image being displayed. Thishas been described in detail above, and thus no further description isgiven.

[0015] 4) only the image signal output from the device of the presenteris displayed, and the images of the other attendants cannot bedisplayed. This has also been described above, and no furtherdescription is given.

[0016] 5) It is impossible to create or edit data from a plurality ofdata and transmit the resultant data to the attendants.

[0017] When a discussion is made among a large number of attendants, itis desirable, in order to achieve high productivity in jobs, not only topresent data of the respective attendants but also to distribute theconclusion of the discussion to the attendants immediately in themeeting. However, the conventional image display device is only capableof displaying one received image signal, and is not capable ofdistributing the data being displayed. Thus, needs described abovecannot be met.

SUMMARY OF THE INVENTION

[0018] In view of the above, it is an object of the present invention toprovide an image display device, a method of controlling an imagedisplay device, and a storage medium on which a program for controllingan image display device is stored, which make it possible to displayat-a-glance views of the contents of input image sources and also makeit possible to quickly switch an image being displayed without causing adisturbance.

[0019] According to an aspect of the present invention, to achieve theabove object, there is provided an image display device comprising aplurality of input terminals for inputting a plurality of image signals,respectively; and combining and displaying means for combining theplurality of image signals input via the input terminals and displayingthe resultant image on the same screen of the display device.

[0020] Preferably, the image display device further comprises selectionmeans for selecting an image signal to be displayed as a main image fromthe image signals combined and displayed on the same screen of thedisplay device; and still state detection means for, when the imagesignal selected as the main image is a signal of a moving image,detecting a period of time during which said moving image is in a stillstate over a predetermined length of time or longer, on the basis of theimage signals, wherein the images other than the main image are updatedwhen the still state detection means detects that the moving image is inthe still state.

[0021] Further objects, features and advantages of the present inventionwill become apparent from the following description of the preferredembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a block diagram illustrating the general configurationof an image display device according to a first embodiment of thepresent invention;

[0023]FIG. 2 is a flow chart illustrating a sub screen displayingprocess executed by the image display device shown in FIG. 1, and moreparticularly, mainly by a CPU thereof;

[0024]FIGS. 3A to 3C are schematic diagrams illustrating examples ofat-a-glance views of input images displayed by the sub screen displayingprocess shown in FIG. 2;

[0025]FIG. 4 is a block diagram illustrating the general configurationof an image display device according to a second embodiment of thepresent invention;

[0026]FIG. 5 is a flow chart illustrating a displaying process executedby the image display device shown in FIG. 4;

[0027]FIG. 6 is a flow chart illustrating a sub screen displayingprocess executed by an image display device according to a thirdembodiment of the present invention;

[0028]FIG. 7 is a flow chart illustrating a sub screen displayingprocess executed by an image display device according to a fourthembodiment of the present invention;

[0029]FIG. 8 is a block diagram illustrating the general configurationof an image display device according to a fifth embodiment of thepresent invention;

[0030]FIG. 9 is a schematic diagram illustrating an example of a mannerof using the image display device shown in FIG. 8;

[0031]FIGS. 10A and 10B are schematic diagrams illustrating a example ofa format for transmission image data and an example of a formation fordisplay mode signal, respectively;

[0032]FIGS. 11A and 11B are schematic diagrams illustrating examples oflayouts of multi screens;

[0033]FIG. 12 is a block diagram illustrating the general configurationof an image display device according to a sixth embodiment of thepresent invention;

[0034]FIG. 13 is a block diagram illustrating the general configurationof an image display device according to a seventh embodiment of thepresent invention; and

[0035]FIG. 14 is a block diagram illustrating an example of aconventional image display device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The present invention is described in further detail below withreference to preferred embodiments in conjunction with the accompanyingdrawings.

[0037]FIG. 1 is a block diagram illustrating the general configurationof an image display device according to a first embodiment of thepresent invention.

[0038] In FIG. 1, a plurality of input terminals 1 for inputting analogimage signals are directly connected to a selector 5 for selecting oneof analog image signals and outputting the selected analog image signal.

[0039] A plurality of input terminals 2 for inputting video signals suchas composite signals are connected to a selector 3, which selects one ofthe video signals input to the selector 3 via the input terminals 2 andoutputs the selected video signal. The output of the selector 3 isconnected to the input of a decoder 4, and the output of the decoder 4is connected to an input of the selector 5.

[0040] The output of the selector 5 is connected to a selector 7 via anA/D converter 6.

[0041] The output of the selector 7 is connected to a signal processingunit 8.

[0042] A memory 9, a D/A converter 10, and a timing controller 14 arealso connected to the signal processing unit 8.

[0043] The output of the D/A converter 10 is connected to a display 11such as an LCD (liquid crystal display).

[0044] A synchronization signal processing circuit 12 is connected, viaa PLL (phase locked loop) circuit 12, to an input of the timingcontroller, and an OSC (oscillator) 15 and a microcomputer (CPU) 16 areconnected to the other inputs of the timing controller 14.

[0045] An image selector 17 is connected to the CPU 16.

[0046] Analog image signals and synchronization signals HD and VD outputfrom a PC (personal computer) or the like are input via the analog inputterminals 1. The video signal input via one of the input terminals 2 isseparated by the decoder 4 into an image signal and synchronizationsignals HD and VD.

[0047] One of the image signals input via the input terminals 1 and 2 isselected by the selectors 3 and 5, and the selected image signal isconverted by the A/D converter 6 into a digital signal and input to thesignal processing unit 8.

[0048] A plurality of video terminals 22 for inputting video signals arealso connected to the selector 7. The selector 7 selects one of thedigital image signals input via the input terminals 22 or the digitalimage signal output from the A/D converter 6. The selected digital imagesignal is output to the signal processing unit 8.

[0049] The signal processing unit 8 adjusts the contrast and thebrightness. The signal processing unit 8 also serves to increase orreduce the size of images in multiscan processing.

[0050] The memory 9 is also used as a buffer memory in the signalprocessing described above.

[0051] The signal output from the signal processing unit 8 is convertedby the D/A converter into an analog signal which is used to drive thedisplay 11.

[0052] Of the image signal and the synchronization signals HD and VDselected by the selector 5, the image signal 5 is input to the A/Dconverter 6. On the other hand, the synchronization signals HD and VDare input to the synchronization signal processing unit 12. Thesynchronization signal processing unit 12 detects the image mode of theinput signal, on the basis of the timing of the synchronization signalsHD and VD. Herein, the detection of the image mode is performed on thebasis of the timing of the synchronization signals HD and VD, and theoscillation frequency of the PLL circuit 13 is determined depending uponthe detected image mode. The image displaying position and the samplingphase are also controlled depending upon the image mode.

[0053] The image selector 17 selects one of input images (to bedisplayed) in accordance with a command given via a remote control unit(not shown) or an external switch (not shown). The image selector 17also displays information about the selection.

[0054] The controlling process executed by the image display deviceconstructed in the above-described manner is described below withreference to FIGS. 2 and 3.

[0055]FIG. 2 is a flow chart illustrating the process of displaying asub screen, executed by the image display device, and more particularlymainly by the CPU 16, according to the present embodiment of theinvention.

[0056] In FIG. 2, if an at-a-glance view start signal is input, writinginto the frame memory is disabled after writing one frame of the currentsignal being processed into the frame memory (step S1 and S2). Herein,the reading of the image signal from the memory and the displaying it onthe display 11 are continued.

[0057] After that, a different image signal is selected by switching theselector 3, and/or the selector 5 (step S3).

[0058] The mode of the image signal is detected on the basis of thevertical synchronization signal VD and the horizontal synchronizationsignal HD of the switched image signal (step S4). In accordance with thedetected mode of the image signal, the setting of the PLL circuit 13,the signal processing unit 8, and the timing controller 14 is performedso as to acquire the image signal in an optimal fashion. (step S5)

[0059] The displaying position and the reduction ratio of the selectedimage are then determined (step S6), and data is written in the memory,at memory addresses corresponding to the determined displaying positionand the reduction ratio (step S7).

[0060] The above process (steps S1 to S7) is performed repeatedly asmany times as there are input images (step S8) thereby displaying theimages arranged in the form of an array to provide an at-a-glance view.

[0061] The above-described sub screen displaying process may beperformed only when an at-a-glance view switch (not shown) is pressed ormay be performed repeatedly at fixed intervals.

[0062] The determination of the mode of the image signal in step S4 maybe performed for each input terminal only when initialization isperformed. In this case, the data representing the modes of the imagesignals input via the respective input terminals or the control datatherefor is stored in a storage device (not shown) disposed in orconnected to the CPU 16 thereby allowing the process to be performed inaccordance with the content stored in the storage device withoutperforming the determination of the mode and without performing thecalculation of the control data associated with the displaying positionadjustment and the sampling phase adjustment of the image signals exceptin the initialization process.

[0063] In this case, because the determination of the mode and thecalculation of the control data for the adjustment of the displayingposition and the sampling phase of the image signals are not performedevery time, it is possible to quickly perform the process of displayingthe sub screen. The contents stored in the storage device may be updatedby reperforming the initial setting.

[0064]FIGS. 3A to 3C illustrate examples of sets of at-a-glance views ofinput images displayed by the above-described sub screen displayingprocess.

[0065]FIG. 3A illustrates an example in which sub screens 11 b to 11 dare displayed below the main screen 11 a. FIG. 3B illustrates an examplein which the screen is divided such that the main screen 11 e and subscreens 11 f to 11 h have the same size. FIG. 3C illustrates an examplein which a plurality of sub screens 11 j to 11 l are overlayed on a mainscreen 11 i.

[0066] Now, an image display device according to a second embodiment ofthe present invention is described below.

[0067] In the first embodiment described above, the at-a-glance views ofthe image signals displayed on the sub screens are updated when a switchis pressed or at fixed intervals. Therefore, if the at-a-glance viewsare updated when a moving image is displayed on the main screen, theupdating operation can cause the moving image to stop the motionthereof, and thus the image becomes unnatural or is disturbed. Thepresent embodiment is intended to solve such a problem.

[0068]FIG. 4 is a block diagram illustrating the general configurationof the image display device of the present embodiment, which isdifferent from the image display device .of the first embodimentdescribed above with reference to FIG. 1 only in that a moving/stillimage detector 21 is added. The moving/still image detector 21 serves todetermine whether the selected image signal is a moving image signal ora still image signal.

[0069]FIG. 5 is a flow chart illustrating the displaying processexecuted by the image display device according to the presentembodiment. In FIG. 5, a main screen is first displayed (step S11).

[0070] After that, it is determined whether a still image has beendisplayed for a predetermined period of time or longer in the mainscreen on the basis of the signal output from the moving/still imagedetector 21 (step S12). If and only if the still image has beendisplayed over the predetermined period of time or longer, a sub screenis displayed (step S13) in a similar manner as described above in thefirst embodiment (FIG. 2), and the process is completed.

[0071] The moving/still image determination is performed on the basis ofthe difference in image data between frames or on the basis of a motionvector calculated from the above difference.

[0072] In the present-embodiment, because the updating of theat-a-glance views of the input images displayed on the sub screen isperformed only when it is determined that a still image has beendisplayed on the main screen over the predetermined period of time orlonger, the updating operation does not cause a problem such as thestopping in motion of the moving image displayed on the main screen, orother artifacts or disturbances in the moving images.

[0073] An image display device according to a third embodiment of thepresent invention is described below.

[0074] The image display device of the third embodiment is differentfrom the image display device of the first embodiment described aboveonly in the sub screen displaying process, and thus the hardware used inthis third embodiment is the same as that shown in FIG. 1.

[0075]FIG. 6 is a flow chart illustrating a sub screen displayingprocess executed by the image display device according to the presetembodiment. The sub screen displaying process according to the presentembodiment is different from that shown in FIG. 2 only in that step S21is added.

[0076] In FIG. 6, when the image mode is detected after switching theimage signal, if it is determined that there is no image signal, theprocess returns to a step (S4→S21→S1) to perform the sub screendisplaying process for the image input via the next input terminalwithout performing the writing into the frame memory.

[0077] In the present embodiment, as described above, when no imagesignal is input via a particular video input terminal, the at-a-glanceview of the image for that terminal is not displayed on the subscreen,and thus the convenience is improved.

[0078] An image display device according to a fourth embodiment of thepresent invention is described below.

[0079] The image display device of the fourth embodiment is differentfrom the image display device of the first embodiment described aboveonly in the sub screen displaying process, and thus the hardware used inthis fourth embodiment is the same as that shown in FIG. 1.

[0080]FIG. 7 is a flow chart illustrating a sub screen displayingprocess executed by the image display device according to the presetembodiment. The sub screen displaying process according to the presentembodiment is different from that shown in FIG. 6 only in that steps S31to S33 are added.

[0081] In FIG. 7, if the result of the image mode detection indicatesthat there is an image signal, the writing into the frame memory isperformed in the normal manner in the sub screen displaying process(steps S21→S5→S6→S7). However, when it is determined that there is noimage signal, a predetermined image is written into the frame memory(steps S21→S31→S32→S33).

[0082] The predetermined image may be registered as follows. The imagewhich is input via the video input terminal and is currently displayedis selected as an image to be registered. Alternatively, the image to beregistered may be selected from the thumbnail images. In this case, whenan image is selected, the selected image may be displayed in an enlargedfashion and registered, or may be maintained in the thumbnail fashion.

[0083] In the present embodiment, as described above, it is determinedwhether the respective input terminals are used or not, on the basis ofthe status of the signals obtained in the initialization process. Thedisplaying of images on the sub screens is not performed, as in thethird embodiment, for the input terminals which are detected asinputting no signals. However, in the case where a particular inputterminals is detected as inputting no signal after the initializationprocess, the last image input via that input terminal of thepredetermined image stored in the memory is displayed. This makes itpossible to maintain the images displayed on the sub screens even when ashort-time loss occurs in the image signals from the connected devices,and thus the convenience is further improved. Because it is possible tospecify the images to be displayed when no image signals are received,the viewability is also improved.

[0084] The reading of the image signal may be performed at the sameframe rate as that of the main selected image or may be performed sothat no distortion is created in the selected main image.

[0085] An image display device according to a fifth embodiment of thepresent invention is described below.

[0086]FIG. 8 is a block diagram illustrating the general configurationof the image display device according to the fifth embodiment.

[0087] In FIG. 8, a wireless transmitting/receiving module 30 includesan antenna 31, a power amplifier (PA) 32, an RF (radio frequency)transceiver 33, a baseband unit 34 including a microcomputer and acommunication protocol processing circuit, and a memory 35 such as aflash EEPROM (electrically erasable and programmable read only memory).The wireless transmitting/receiving operation may be preferablyperformed using a 2.4 GHz band according to the technique based on theBluetooth, IEEE802.11, IEEE802.11a, IEEE802.11b, or the like. For thepurpose of achieving widespread use, the Bluetooth technique is designedsuch that most software resources according to the IrDA (Infrared DataAssociation) standard may also be used in the Bluetooth technique. Inthe Blutooth technique, an object exchange protocol (OBEX) is employedso that application software can exchange objects regardless of thedifference in the type of devices.

[0088] Data and a control signal are transmitted via a bus 41 to amicrocomputer 42 of the main unit of the image display device. A USB(Universal Serial Bus) or a PCI (Peripheral Component Interconnect) busmay be employed as the interface bus 41. An image signal according tothe NTSC (National Television System Committee) standard or an imagesignal output from a PC is input to a selector 44 via a video inputterminal 43. The output of the selector 44 is switched by an inputselector 45.

[0089] The output of the selector 44 is connected to a signal processingunit 46 and a PLL circuit 47. The signal processing unit 46 is alsoconnected to a memory 48 an a timing controller 49. The outputs of thesignal processing unit 46 are connected, directly or via a D/A converter50, to a display 51.

[0090] Preferably, the display 51 is a TFT LCD or a DMD. When a DMD isemployed as the display 51, the D/A converter 50 is replaced with a DMDdriver.

[0091] The image display device also includes a displaying positiondetector 52.

[0092] Before describing the operation of the image display device ofthe present embodiment, an example of a manner of using the imagedisplay device of the present embodiment is described with reference toFIG. 9.

[0093]FIG. 9 illustrates an example of a manner in which a meeting isheld. A notebook PCs 62 to 64, an ink-jet printer 65, a scanner 66, anda projector 67 are disposed on a table 61. Each of these devicesincludes a wireless communication module 30 of the above-described type.

[0094] An image is projected onto a screen 70 by the projection 67.Outdoors in the outside of the meeting room, a digital camera 30 is usedto take an image of a car 81. The image taken by the digital camera 80can be transmitted using a portable telephone (not shown). A portabletelephone 68 for receiving the image data taken by the digital camera 80is disposed on the table 61.

[0095] The meeting is attended by a total of four persons, that is, Mr.A who has the digital camera 80 and who is present at a remote location,Mr. B having the notebook PC 62, Mr. C having the notebook PC 63, andMr. D having the notebook PC 64. Mr. B, who is a host of the meeting,provides a list of devices which are accessible by means of wirelesscommunication and which are used in the meeting. Of the devices placedon the table 61, the notebook PC 63 of Mr. C, the notebook PC 64 of Mr.D, the printer 65, the scanner 66, the projector 67, and the portabletelephone 68 are selected as devices used in the meeting and they areconnected to each other via a LAN (Local Area Network). Mr. A, who wasasked in advance via a telephone call to attend the meeting, is nowattending the meeting via the portable telephone. In this case, forexample, the PC 62 of Mr. B is currently used as a master device in theLAN system and the other devices are used as slave devices. Theprojector 67 displays data received from the connected devices in such amanner that the data output from the Mr. B's PC is displayed in an area70 a, data 63 a displayed on the Mr. C's PC 63 is displayed in an area70 b, data 64 a displayed on the Mr. D's PC 64 is displayed in an area70 c, data 66 a read by the scanner 66 is displayed in an area 70 d, thecurrent status of the printer 65 is displayed in an area 70 e, and thepicture of the car 81 taken by the digital camera 80 at the remotelocation and received via the portable telephone is displayed in an area70 f.

[0096] As described above, the projector 67 displays images according tothe data output from those devices which are connected using theirwireless communication module 30 to each other via the network and whichare controlled by the master device so as to act as slave devices in thenetwork system. Thus, it is possible for the devices used in the meetingto easily acquire data from other connected devices, and data can beeasily output to the printer.

[0097] Of the data input to the projector 67, the image data output fromthe master device is displayed in an display area 70 a. If the masterdevice is switched from the device of Mr. B to some device of Mr. A, C,or D, the image of the new master device is displayed in the displayarea 70 a. The switching of the master device may-be performed not onlyby the respective terminals but also by operating a pointer (not shown)or a digitizer (not shown) coupled with the projector 67. That is, aselected image is displayed in a large display area, and images ofnon-selected terminals connected via the network are displayed in smalldisplay areas. In this system, if some data is modified during themeeting, the modified data may be transmitted to the respectiveterminals connected via the wireless network. Although in the presentembodiment described above, the image data of a device selected as themaster device is displayed in the main display area, the selection ofthe image data to be displayed in the main display area and the changein the size of images displayed in the respective display areas may alsobe performed by transmitting display mode information to the projector67 from a slave device.

[0098] Referring back to FIG. 8, the control operation in this system isdescribed. The circuit shown in FIG. 8 is embedded in the projector 67.As describe above with reference to FIG. 9, after turning on theelectric power of the respective devices using in the meeting, slavedevices are selected using a device selected as an initial masterdevice. When these devices are selected, device addresses on the networkare assigned to the respective devices. The projector 67 receives, viathe antenna 31, image data or control data output from the devicesconnected to the network. The data output from each device includes dataindicating whether the device is a master or slave, that is, dataidentifying the terminal device, image data, signals (synchronizationsignals HD and VD) which define the timing of the image data, and thestatus of the device such as the printer 65. A data signal is extractedfrom a RF carrier waver by means of decoding via the RF transceiver 33and the baseband unit 34, and the obtained data in the form of a serialdigital signal is applied to the microcomputer 42 via the bus 41.

[0099] The microcomputer 42 determines which terminal device the imagedata, or control data is received from, and the microcomputer 42 writesthe received data into the memory 48, at proper addresses. When theprojector 67 receives image data or control data from a plurality ofterminal devices, the data is written in different memory areas, of thememory 48, assigned to the respective terminal devices so that they areintegrated in a single image signal when read from the memory 48.

[0100] Although in the present embodiment, the memory 48 used in theimage processing but is also used as a memory for temporarily storingthe image data or the control data, an additional memory may be disposedbetween the bus 41 and the microcomputer 42 so that the image data orthe control data received from the plurality of terminal devices isfirst stored in the additional memory temporarily and then transferredto the memory 48.

[0101] In addition to the data input via the wireless communicationmodule 30, data such as an analog signal output from a PC or an analogvideo signal is also input via the video input terminals 43 and appliedto the selector 44 via an A/D converter (not shown). The video inputterminals 43 are not limited to the analog terminals, and a digitalterminal (LVDS, TMDS) may also be employed.

[0102] The input selector 45 selects one of signals input via the videoinput terminals 43, and the selected signal is stored in the memory 48via the signal processing unit 46.

[0103] The signal processing unit 46 converts the image data acquiredvia the two paths described above into a signal (in accordance with adot clock) in a form which matches the display 51 and reduces respectiveimages to the sizes corresponding to the small display areas as shown inFIG. 9. The plurality of the image data are then combined together, andthe resultant RGB signal output from the signal processing unit 46 isconverted into a analog signal, which drives the display 51. Thus, atleast two image signals are combined together and displayed on a singlescreen.

[0104] The displaying position detector 52 detects the first and lastsynchronization signals and properly controls the displaying position inaccordance with the detected synchronization signals. The displayingposition detector 52 also adds synchronization signals HD and VD to thesignal which has been selected by the input selector 45 and which hasbeen processed by the signal processing unit 46, wherein themicrocomputer 42 sets the frequency of the PLL circuit 47.

[0105] The transmission image data and the display mode signal aredescribed, which are transmitted from PCs 62, 64 or the like and used todetermine the images to be displayed and the layout of images displayedby the projector 67.

[0106] Driver software for driving the projector 67 is installed, inadvance, in the respective PCs 62-64 and peripheral devices 65-68 shownin FIG. 9, information about the display size and the number of pixelsof the projector is stored therein.

[0107] In order to display image data associated with a master or slavedevice via the projector 67, an image display command output icondisplayed by the driver software on the screen of each PC 62-64 isturned on. When the image display command output icon is in theon-state, the image information displayed on the respective PCs 62-64are converted by the driver software into a form which matches theprojector 67 and sent to the projector 67.

[0108] Alternatively, to achieve the same purpose, a data output(transmission) switch may be provided.

[0109]FIG. 10A illustrates an example of the format of the transmissionimage data, and Fig. 10B illustrates an example of the format of thedisplay mode signal.

[0110] In FIG. 10A, the transmission image data includes the address ofa transmitting device, the address of a receiving. device, an image datastart signal, header information, image data, and an image data endsignal, wherein the header information includes data representing theimage size, the compression scheme, the compression rate, and the imageformat.

[0111] When the projector 67 receives the transmission image data viathe antenna 31, the data is stored in the memory 48 via the bus 41.Herein, in accordance with the header information, decompression andincreasing/decreasing of the size of the image are performed and theaddresses of the memory where the data is written are determined.

[0112] The projector 67 can change the displaying positions and thesizes of the plurality of images in response to a display mode signalreceived from the master or slave device via the antenna 31.

[0113] In Fig. 10B, the display mode signal includes layout informationsuch as a display mode start signal, data representing the positionswhere the respective images are to be displayed, data representing thesize of the respective images, data indicating the selected image, anddisplay mode end signal. Alternatively, the display mode signal mayinclude data specifying a display mode selected from a plurality ofmodes available in the display device.

[0114] In the present embodiment, as described above, images displayedon the screen can be freely selected by the master or slave device. Thisprovides a great convenience.

[0115] The conventional display device is only capable of displayinginput image signals. In contrast, the system according to the presentinvention has a further capability as described below.

[0116] A plurality of terminal devices each having a module similar tothe wireless communication module 30 for transmitting an image signal tothe image display device are connected to the network, and the networkenvironment is established such that a mater terminal device and slaveterminal devices controlled by the master device are defined in thenetwork. In order to display the data associated with a terminal deviceconnected to the network, it is required to transmit the data from thatterminal device to the projector 67. In the present embodiment, theimage from the master terminal device or the image input via the videoinput terminal is employed as the selected image, and when the imagesignal period of image signals transmitted from at least two devices isrepresented by T, the transmission period of the selected image signalis represented by τ, the number of non-selected image signals isrepresented by n, and a constant k (≧) is given, the parameters T, τ, n,and k are set such that the following equation is satisfied:

τ=kT/(n+k)

[0117] Non-selected data is acquired during the remaining period (T−τ).Thus, the data acquisition ratio of the selected data to that of thenon-selected data is set to k, which allows the synthesized image to beformed with selected data having high quality and non-selected datacompressed by a high compression ratio thereby achieving a high-qualitysynthesized image with no artifact. From the above viewpoint, it isdesirable to determine the value of k depending upon the ratio of theimage sizes. Each non-selected data is acquired during a period of about(T−τ)/n, wherein the acquiring period is not necessarily equal for allnon-selected data because the data size can be different. As the valueof the constant k increases from “1”, the ratio of the period of timeduring which the data is received from the master terminal device to theperiod of time during which data is received from the slave terminaldevices increases, and thus the quality of the selected image increases.The determination as to whether the image from the master terminaldevice or the image input via the video input terminal is employed asthe selected image, is made according to a switching operation performedusing a remote control unit of the widely-used type (not shown). Thetechnique described above is very useful to quickly display desired datawith high quality, in particular when the transmission capacity of thecommunication line such as the wireless communication line is limited.The transmission rate of the transmission of data from slave terminaldevices may be reduced by transmitting only headline data or partiallyremoving the image data in a systematic fashion and transmitting theremaining data. In any case, when image data is transmitted from theslave terminal devices, the transmission is performed after convertingthe image data into a form which is compressed by a greater ratio thanthat of the image data from the master terminal device. When it isdesired to view the details of an image transmitted from a slaveterminal device, the slave terminal device is switched to the masterterminal device by the display device or the current master terminaldevice.

[0118] The technique of transmitting data to the display device such asthe projector according to the present invention has been describedabove. Now a technique of temporarily storing data in a memory andprocessing the data before displaying it is described below.

[0119] The data received via the wireless communication module or viathe video input terminal 43 is stored in the memory 48. When image datais synthesized from the selected image data and the non-selected imagedata stored in the memory 48, the non-selected image data is compressedwith a great compression ratio so as to achieve the effects similar tothose described above.

[0120] The control operation performed by the image display deviceconstructed in the above-described manner is described below.

[0121] When an at-a-glance view start signal is input, either the masterterminal device or the video input terminal, which is set as a defaultdevice, is first selected. If desired, the selected device may beswitched by operating the remote control unit or the like. After writingone frame of image data received from the above device, the writing intothe memory is temporarily disabled. However, the reading of the imagesignal from the memory and the displaying of the image signal on thedisplay may be continued. In this case, only the same one frame of imagedata is displayed.

[0122] Information (information representing the status of the devicesuch as the printer as well as the image data) is also transmitted fromthe connected terminal devices to the image display device, from oneterminal device to another. In this transmission process, the amount ofdata transmitted device by device is not necessarily limited to oneframe. Before acquiring the image data, icons or the like correspondingto the respective terminals are displayed instead of the real imagedata. When compressed data to be displayed in desired display areas hasbeen acquired in the above-process, the icons are switched to the realimage data. Alternatively, a combination of icons and real data may bedisplayed.

[0123] The layout of a multiscreen layout is then determined.

[0124]FIGS. 11A and 11 B illustrate examples of multiscreen layout. Inthe example shown in FIG. 11A, an area 70B on the left side of thescreen and an area 70C at the bottom of the screen are set as defaultnon-selected image display areas. These non-selected image display areasvary depending upon the number of non-selected images. The selectedimage is displayed in the remaining area 70A. When there are a smallnumber of non-selected images, the non-selected image display area 70Dis automatically reduced as shown in FIG. 11B, and the selected imagedisplay area 70A is shifted toward the center of the screen, dependingupon the aspect ration. The above-described layout is defined bydefault, and the layout can be modified by a user in a similar manner tothat in which the size of a window displayed on a PC is modified.

[0125] After determining the layout in the above-described manner, thepositions where the image data acquired from the respective terminaldevices is to be displayed are determined, and the image data iscompressed (reduced) depending upon the image sizes.

[0126] The data is acquired from one terminal device to another duringthe image acquisition period with the above-described ratio, and theacquired data is written in the memory at the corresponding memoryaddresses.

[0127] The above process is performed repeated as many times as thereare images thereby displaying the images arranged in the form of anarray to provide an at-a-glance view.

[0128] An image display device according to a sixth embodiment of thepresent invention is described below.

[0129] The image display device of the present embodiment is differentfrom that of the fifth embodiment described above in that the display51, the D/A converter 50, and the displaying position detector 52 areremoved. That is, unlike the fifth embodiment in which the wirelesscommunication module 30 is embedded in the projector 67, the device ofthe sixth embodiment includes only the wireless module 30 and the partfor selecting one of a plurality of input signals.

[0130]FIG. 12 is a block diagram illustrating the general configurationof the image display device according to the present embodiment. Asshown in FIG. 12, the image display device includes digital outputterminals 55 for outputting a digital signal representing an imagesynthesized from a plurality of input image signals.

[0131] By connecting this device to a conventional front projectorhaving only one PC terminal and one video terminal, it becomes possiblefor the projector to handle a plurality of input image signals in thewireless communication environment.

[0132] A plurality of LAN cable terminals for the 10 Base-T or 100Base-T connection may be provided so that the image display device hasthe hub capability for connecting a network temporarily formed usingwireless communication modules with an existing LAN.

[0133] An image display device according to a seventh embodiment of thepresent invention is described below.

[0134] The image display device of the seventh embodiment is differentfrom the image display device of the fifth embodiment described aboveonly in that a moving/still image detector is added.

[0135]FIG. 13 is a block diagram illustrating the general configurationof the image display device according to the present embodiment. Asshown in FIG. 13, the moving/still image detector 56 determines whetherthe image data received from each terminal device is moving image dataor still image data on the basis of the difference in image data betweenframes or on the basis of a motion vector calculated from the abovedifference. That is, the amount and the type of the image data receivedfrom the respective terminal devices are determined by the moving/stillimage detector 56, and the data acquisition ratio is adjusted dependingupon the detected amount and type of the data. When the image datareceived from the master device or the image data input via the videoinput terminal is moving image data or a semi-moving image data, thevalue of the constant k described earlier is adjusted so that theresultant displayed image becomes natural. (Herein, the semi-movingimage refers to an image including a moving part or a still image whichis switched from time to time). Conversely, when the image data receivedfor a predetermined period of time or longer from the master device orthe image data input via the video input terminal is still image dataand when non-selected images are great in data amount, the dataacquisition ratio for the non-selected images is increased so asto-obtain a synthesized image with higher quality.

[0136] In the present embodiment, a printer 65 for outputting an imageis used as one of devices connected to the network via their wirelesscommunication modules also include, in addition to the PCs 62-64, thevideo cameral, and the scanner 66, for transmitting an image to theprojector 67. An icon corresponding to the output device such as theprinter 65 is displayed in a particular area on the screen. When it isdesired to print a particular image during a meeting, if the icon isclicked, a print setting screen is displayed in an overlayed fashionthereby allowing a user to specify a file to be printed and printingconditions. Thus, it is possible to print the image immediately whenprinting is required, without having to connect the printer via a cable.

[0137] Note that the objects of the present invention may also beachieved by supplying a storage medium, on which a software programimplementing the functions of any of the embodiments described above isstored, to a system or a device whereby a computer (CPU or MPU) in thesystem or the device reads and executes the program code stored on thestorage medium.

[0138] In this case, it should be understood that the program code readfrom the storage medium implements the novel functions of invention andthus the storage medium storing the program code falls within the scopeof present invention.

[0139] Specific examples of such a storage medium for storing theprogram code include a floppy disk, a hard disk, an optical disk, amagneto-optical disk, a CD-ROM, CD-R, a magnetic tape, a non-volatilememory card, and a ROM. The program code may be supplied from a servercomputer via a communication network.

[0140] Furthermore, the scope of the present invention includes not onlysuch a system in which the functions of any embodiment described aboveis implemented simply by reading and executing a program code on acomputer but also a system in which a part of or the whole of processinstructed by the program code is performed using an OS (operatingsystem) on the computer.

[0141] Furthermore, the scope of the present invention also includes asystem in which a program code is transferred once from a storage mediuminto a memory provided in a function extension board inserted in acomputer or provided in a function extension unit connected to thecomputer, and then a part of or the whole of process instructed by theprogram code is performed by a CPU or the like in the function extensionboard or the function extension unit thereby implementing the functionsof any embodiment described above.

[0142] In the present embodiment, as described above, the modes of therespective image signals input via the plurality of input terminals areconverted to a mode which is optimum for the image display device todisplay the image signals, and the plurality of converted image signalsare combined and displayed on the same screen of the display device sothat the contents of the input image signals can be easily viewed.

[0143] The modes of the image signals received via thetransmitting/receiving means are converted to a mode which is optimumfor the display device to display the image signals, and the pluralityof converted image signals or the control signal received via thetransmitting/receiving means are combined and displayed on the samescreen of the display device thereby making it possible to input aplurality of image signals without needing a cable connection.

[0144] While the present invention has been described with reference towhat are presently considered to be the preferred embodiments, it is tobe understood that the invention is not limited to the disclosedembodiments on the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

What is claimed is:
 1. An image display device comprising: a pluralityof input terminals for inputting a plurality of image signals,respectively; and combining and displaying means for combining saidplurality of image signals input via the input terminals and displayingthe resultant image on the same screen of a display device.
 2. An imagedisplay device according to claim 1, further comprising at-a-glance viewproviding means for combining and displaying said image signals withpredetermined timing using said combining and displaying means so as toprovide at-a-glance views of the contents of said plurality of imagesignals input via said plurality of input terminals.
 3. An image displaydevice according to claim 2, further comprising decision means forconverting the modes of the respective image signals input via the inputterminals into a mode suitable for said image display device to displaythe image signals, wherein when the at-a-glance views of the contents ofthe respective image signals are provided for the first time by saidat-a-glance view providing means, the modes of the respective imagesignals or the control data thereof are stored in storage means, andwhen the at-a-glance views are provided at any time other than the firsttime, said mode conversion and said process of combining and displayingthe image signals are-performed by said conversion means and saidcombining and displaying means in accordance with the contents stored insaid storage means.
 4. An image display device according to claim 2,further comprising-detection means for detecting whether there is aninput image signal for each of the plurality of input terminals; andcontrol means for controlling said conversion means and said combiningand displaying means so as not to perform said conversion and saidcombining and displaying process for an input terminal which isdetected, by said detection means, as inputting no image signal when theat-a-glance views of the contents of the image signals are provided forthe first time.
 5. An image display device according to claim 2, furthercomprising an operation control unit which is operated by a user,wherein said timing is given when said operation control unit isoperated by the user.
 6. An image display device according to claim 2,further comprising signal generation means for generating a signal atpredetermined periodic intervals, wherein said timing is given when saidsignal is generated by the signal generation means at the predeterminedperiodic intervals.
 7. An image display device-according to claim 2,further comprising: selection means for selecting an image signal to bedisplayed as a main image from the image signals combined and displayedon the same screen of said display device; and still state detectionmeans for, when the image signal selected as the main image is a signalof a moving image, detecting a period of time during which said movingimage is in a still state over a predetermined length of time or longer,on the basis of said image signals, wherein said timing is given whensaid still state detection means detects that the moving image is in thestill state.
 8. An image display device according to claim 4, furthercomprising storage means for storing, in advance, predetermined imagedata, wherein if said detection means detects that there is an imagesignal input via a particular input terminal when said at-a-glance viewproviding means performs the at-a-glance view providing process for thefirst time but if said detection means detects that there is no imagesignal input via said particular input terminal in the at-a-glance viewproviding process performed later by said at-a-glance view providingmeans, said control means performs the control operation such that theimage data stored in said storage means is read as the image signal forsaid input terminal and said image data is used as one of image signalscombined and displayed by said combining and displaying means.
 9. Animage display device according to claim 8, wherein said predeterminedimage data is the image signal which is input via each input terminalbefore said detection means detects that there is no input image signal.10. An image display device according to claim 8, wherein saidpredetermined image data is an image signal having no relationship withthe image signal which is input via each input terminal.
 11. An imagedisplay device according to claim 1, further comprising compressionmeans for compressing image signals which are combined and displayed onthe same screen of said display device, wherein said compression meanscompresses image signals, which are included in the image signalscombined and displayed on the same screen of said display device butwhich are not selected as the main image, with a compression ratiogreater than the compression ratio for an image signal selected as themain image from the image signals combined and displayed on the samescreen of said display device.
 12. A plurality of terminal devices whichare connected via a wireless network to an image display deviceaccording to claim 1 such that an image signal is transmitted to saidimage display device from each terminal device, each terminal deviceincluding transmitting and receiving means for transmitting andreceiving an image signal or a control signal by means of wirelesscommunication, said terminal being characterized in that: when the imagesignal period of image signals transmitted from at least twotransmitting and receiving means is represented by T, the transmissionperiod of an image signal selected as the main image from the imagesignals combined and displayed on the same screen of the display deviceis represented by τ, the number of image signals which are combined anddisplayed on the same screen of the display device and which are notselected as the main image is represented by n, and a constant k isgiven, the parameters T, τ, n, and k are set such that the followingequation is satisfied: τ=kT/(n+k)
 13. A terminal device according toclaim 12, further comprising compression means for compressing saidimage signal to be transmitted, wherein said compression meanscompresses an image signal, which is included in the image signalscombined and displayed on the same screen of said display device butwhich is not selected as the main image, with a compression ratiogreater than the compression ratio for an image signal selected as themain image from the image signals combined and displayed on the samescreen of said display device.
 14. A terminal device including adecision means for determining one of the plurality of terminal devicesaccording to claim 12 as a master terminal device and the remainingterminals devices as slave terminal devices, wherein an image signaltransmitted from a terminal device determined as the master terminaldevice by said decision means is selected as the main image among theimage signals which are combined and displayed on the same screen ofsaid display device.
 15. A method of controlling an image displaydevice, comprising the steps of: inputting a plurality of image signalsvia a plurality of input terminals; and displaying the plurality ofinput image signals on the same screen of the display device.
 16. Amethod of controlling an image display device, according to claim 15,further comprising the step of combining and displaying said imagesignals with predetermined timing so as to provide at-a-glance views ofthe contents of said plurality of image signals input via said pluralityof input terminals.
 17. A method of controlling an image display device,according to claim 16, further comprising the step of converting themodes of the respective input image signals into a mode suitable forsaid display device to display the image signals, wherein when theat-a-glance views of the contents of the respective image signals areprovided for the first time, the modes of the respective image signalsor the control data thereof are stored in storage means, and when theat-a-glance views are provided at any time other than the first time,said mode conversion and said process of combining and displaying theimage signals are performed in accordance with the contents stored insaid storage means.
 18. A method of controlling an image display device,according to claim 16, further comprising the step of detecting whetherthere is an input image signal for each of said plurality of inputterminals when the contents of said image signals are displayed so as toprovide the at-a-glance views thereof, wherein said mode conversion andsaid process of combining and displaying the image data are performedfor an input terminal which is detected, in said detection step, asinputting no image signal when the at-a-glance views of the imagesignals are provided for the first time.
 19. A method of controlling animage display device, according to claim 16, wherein said timing isgiven when an operation control unit is operated by a user.
 20. A methodof controlling an image display device, according to claim 16, whereinsaid timing is given when a signal is generated by a signal generationmeans at predetermined periodic intervals.
 21. A method of controllingan image display device, according to claim 16, further comprising thesteps of: selecting an image signal to be displayed as a main image fromthe image signals combined and displayed on the same screen of saiddisplay device; and when the image signal selected as the main image isa signal of a moving image, detecting a period of time during which saidmoving image is in a still state over a predetermined length of time orlonger, on the basis of said image signals, wherein said predeterminedtiming is given when the moving image is detected as being in the stillstate.
 22. A method of controlling an image display device, according toclaim 18, further comprising the step of storing, in advance,predetermined image data, wherein if it is detected in said detectionstep that there is an image signal input via a particular input terminalwhen said at-a-glance view providing step is performed for the firsttime but if it is detected in said detection step that there is no imagesignal input via said particular input terminal when said at-a-glanceview providing step is performed at any time other than the first time,the image data stored in said storage means is read as the image signalfor said input terminal and said, image data is used as one of imagesignals which are combined and displayed.
 23. A method of controlling animage display device, according to claim 22, wherein said predeterminedimage data is the image signal which is input via each input terminalbefore it is detected in said detection step that there is no inputimage signal.
 24. A method of controlling an image display device,according to claim 22, wherein said predetermined image data is an imagesignal having no relationship with the image signal which is input viaeach input terminal.
 25. A method of controlling a plurality of terminaldevices according to claim 12, comprising the steps of: determining oneof said plurality of terminal devices as a master terminal device andthe remaining terminal devices as slave terminal devices; and employingan image signal, transmitted from the terminal device determined in saiddetermination step as the master terminal device, as a main imageselected from image signals which are combined and displayed on the samescreen of said display device.
 26. A storage medium including acomputer-executable program stored thereon, said program including aprocess of controlling an image display device, said process comprisingthe steps of: inputting a plurality of image signals via a plurality ofinput terminals; and displaying the plurality of input image signals onthe same screen of the display device.
 27. A storage medium according toclaim 26, said process further comprising the step of combining anddisplaying said image signals with predetermined timing so as to provideat-a-glance views of the contents of said plurality of image signalsinput via said plurality of input terminals.
 28. A storage mediumaccording to claim 27, said process further comprising the step ofconverting the modes of the respective input image signals into a modesuitable for said display device to display the image signals, whereinwhen the at-a-glance views of the contents of the respective imagesignals are provided for the first time, the modes of the respectiveimage signals or the control data thereof are stored in storage means,and when the at-a-glance views are provided at any time other than thefirst time, said mode conversion and said process of combining anddisplaying the image signals are performed in accordance with thecontents stored in said storage means.
 29. A storage medium according toclaim 27, said process further comprising the step of detecting whetherthere is an input image signal for each of said plurality of inputterminals when the contents of said image signals are displayed so as toprovide the at-a-glance views thereof, wherein said mode conversion andsaid process of combining and displaying the image data are performedfor an input terminal which is detected, in said detection step, as,inputting no image signal when the at-a-glance views of the imagesignals are provided for the first time.
 30. A storage medium accordingto claim 27, wherein said timing is given when an operation control unitis operated by a user.
 31. A storage medium according to claim 27,wherein said timing is given when a signal is generated by a signalgeneration means at predetermined periodic intervals.
 32. A storagemedium according to claim 27, said process further comprising the stepsof: selecting an image signal to be displayed as a main image from theimage signals combined and displayed on the same screen of said displaydevice; and when the image signal selected as the main image is a signalof a moving image, detecting a period of time during which said movingimage is in a still state over a predetermined length of time or longer,on the basis of said image signals, wherein said predetermined timing isgiven when the moving image is detected as being in the still state. 33.A storage medium according to claim 29, said process further comprisingthe step of storing, in advance, predetermined image data, wherein if itis detected in said detection step that there is an image signal inputvia a particular input terminal when said at-a-glance view providingstep is performed for the first time but if it is detected in saiddetection step that there is no image signal input via said particularinput terminal when said at-a-glance view providing step is performed atany time other than the first time, the image data stored in saidstorage means is read as the image signal for said input terminal andsaid image data is used as one of image signals which are combined anddisplayed.
 34. A storage medium according to claim 33, wherein saidpredetermined image data is the image signal which is input via eachinput terminal before it is detected in said detection step that thereis no input image signal.
 35. A storage medium according to claim 33,wherein said predetermined image data is an image signal having norelationship with the image signal which is input via each inputterminal.
 36. A storage medium including a computer-executable programstored thereon, said program including a process of controlling an imagedisplay device, said process comprising the steps of: determining one ofsaid plurality of terminal devices as a master terminal device and theremaining terminal devices as slave terminal devices; and employing animage signal, transmitted from the terminal device determined in saiddetermination step as the master terminal device, as a main imageselected from image signals which are combined and displayed on the samescreen of said display device.